Financial Instruments (Fair Value Of Investments) (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Marketable investment securities available for sale in an unrealized loss position
In Loss Position for Less Than 12 Months, Fair Value	$ 35,927	$ 61,701
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	12	136
In Loss Position for More Than 12 Months, Fair Value	0	0
In Loss Position for More Than 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	35,927	61,701
Total, Gross Unrealized Losses	12	136
Corporate
Marketable investment securities available for sale in an unrealized loss position
In Loss Position for Less Than 12 Months, Fair Value	29,844	38,276
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	11	124
In Loss Position for More Than 12 Months, Fair Value	0	0
In Loss Position for More Than 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	29,844	38,276
Total, Gross Unrealized Losses	11	124
Government agency
Marketable investment securities available for sale in an unrealized loss position
In Loss Position for Less Than 12 Months, Fair Value	6,083	23,425
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	1	12
In Loss Position for More Than 12 Months, Fair Value	0	0
In Loss Position for More Than 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	6,083	23,425
Total, Gross Unrealized Losses	$ 1	$ 12